Local spam filtering still works quite fine. It just needs a lot of data most users probably don't have when starting out.
I just use bogofilter, and it worked almost perfectly from the start, just because I saved years upon years of SPAM and HAM. 10's of thousands of messages each.
It got slightly worse over years, because I incrementally only train it on new SPAM but not on new HAM, because of laziness.
People probably have HAM archives, but don't usually save their SPAM, to be able to start using Bayesian spam filters right away with great results.
Personally I find it much better than whatever Google uses. I don't even bother with SMTP level domain/IP blacklists, or reverse IP/domain checks anymore. All mail is just passed right to the mailbox and is then pre-filtered by a bogofilter to SPAM folder that I check once weekly, and barely find any HAM there. I receive about 500k mails a year.
I just use bogofilter, and it worked almost perfectly from the start, just because I saved years upon years of SPAM and HAM. 10's of thousands of messages each.
It got slightly worse over years, because I incrementally only train it on new SPAM but not on new HAM, because of laziness.
People probably have HAM archives, but don't usually save their SPAM, to be able to start using Bayesian spam filters right away with great results.
Personally I find it much better than whatever Google uses. I don't even bother with SMTP level domain/IP blacklists, or reverse IP/domain checks anymore. All mail is just passed right to the mailbox and is then pre-filtered by a bogofilter to SPAM folder that I check once weekly, and barely find any HAM there. I receive about 500k mails a year.